The present study was aimed to demonstrate that cytochrome P-450 was induced by drug administration in particular tissues in the eye. Phenobarbital was used as an inducer. We showed immunohistochemically that cytochrome P-450 was induced in the cornea, conjunctiva and ciliary epithelium of rabbits after four days of intraperitoneal administration of phenobarbital at a dose of 80 mg per kg per day. We did not detect significant immunofluorescence in other ocular tissues. Prolonged administration caused degeneration of the ciliary epithelium, but no pathological change was seen in other ocular tissues. In this case, immunofluorescence was not detected in the ciliary epithelium but in the cornea, conjunctiva and lens.